Ggplot doesn't draw lines of communication between the group means more?

Question

I seem to have missed a change in how ggplot2 works. I have an example from a statistics textbook (A. Field (2012), “Detecting Statistics Using R, p. 593”), which I am sure has worked, but now does not create communication lines between grouped data tools.

Here are some sample data:

participant<-gl(20, 9, labels = c("P01", "P02", "P03", "P04", "P05", "P06", "P07", "P08", "P09", "P10", "P11", "P12", "P13", "P14", "P15", "P16", "P17", "P18", "P19", "P20" )) drink<-gl(3, 3, 180, labels = c("Beer", "Wine", "Water")) imagery<-gl(3, 1, 180, labels = c("Positive", "Negative", "Neutral")) groups<-gl(9, 1, 180, labels = c("beerpos", "beerneg", "beerneut", "winepos", "wineneg", "wineneut", "waterpos", "waterneg", "waterneut")) attitude<-c(1, 6, 5, 38, -5, 4, 10, -14, -2, 26, 27, 27, 23, -15, 14, 21, -6, 0, 1, -19, -10, 28, -13, 13, 33, -2, 9, 7, -18, 6, 26, -16, 19, 23, -17, 5, 22, -8, 4, 34, -23, 14, 21, -19, 0, 30, -6, 3, 32, -22, 21, 17, -11, 4, 40, -6, 0, 24, -9, 19, 15, -10, 2, 15, -9, 4, 29, -18, 7, 13, -17, 8, 20, -17, 9, 30, -17, 12, 16, -4, 10, 9, -12, -5, 24, -15, 18, 17, -4, 8, 14, -11, 7, 34, -14, 20, 19, -1, 12, 43, 30, 8, 20, -12, 4, 9, -10, -13, 15, -6, 13, 23, -15, 15, 29, -1, 10, 15, 15, 12, 20, -15, 6, 6, -16, 1, 40, 30, 19, 28, -4, 0, 20, -10, 2, 8, 12, 8, 11, -2, 6, 27, 5, -5, 17, 17, 15, 17, -6, 6, 9, -6, -13, 30, 21, 21, 15, -2, 16, 19, -20, 3, 34, 23, 28, 27, -7, 7, 12, -12, 2, 34, 20, 26, 24, -10, 12, 12, -9, 4) longAttitude<-data.frame(participant, drink, imagery, groups, attitude) 

And here is the plot code:

 library(ggplot2) attitudeInt <- ggplot(longAttitude, aes(drink, attitude, colour = imagery)) attitudeInt + stat_summary(fun.y = mean, geom = "point") + stat_summary(fun.y = mean, geom = "line", aes(group = imagery)) + stat_summary(fun.data = mean_cl_boot, geom = "errorbar", width = 0.2) + labs(x = "Type of Drink", y = "Mean Attitude", colour = "Type of Imagery") 

Isn't it that the stat_summary(fun.y = mean, geom="line", aes(group = imagery)) part stat_summary(fun.y = mean, geom="line", aes(group = imagery)) should draw these particular lines of communication?

Thank you for your help.

Answer 1

This will not solve the problem in ggplot2 , but it is a workaround.

Summarize your data first. As in the source code, you used mean_cl_boot to calculate confidence intervals, and then used in this example.

 library(plyr) dfAtt<-ddply(longAttitude,~drink+imagery,function(x) mean_cl_boot(x$attitude)) dfAtt drink imagery y ymin ymax 1 Beer Positive 21.05 15.65000 26.90750 2 Beer Negative 4.45 -2.60125 12.00000 3 Beer Neutral 10.00 5.49750 14.75000 4 Wine Positive 25.35 22.40000 28.25000 5 Wine Negative -12.00 -14.40000 -9.49875 6 Wine Neutral 11.65 8.95000 14.40125 7 Water Positive 17.40 14.40000 20.45000 8 Water Negative -9.20 -12.25000 -6.34875 9 Water Neutral 2.35 -0.75125 4.90000 

Then write down your data:

 ggplot(dfAtt, aes(x=drink, y=y, colour=imagery,group=imagery)) + geom_errorbar(aes(ymin=ymin, ymax=ymax), width=.2) + geom_line() + geom_point() + labs(x = "Type of Drink", y = "Mean Attitude", colour = "Type of Imagery") 

Answer 2

As Brian Diggs pointed out that this is a known bug that has been fixed recently. Thus, updating ggplot2 to 0.9.3.1 or higher should result in the proper line building in stat_summary.